A plasma spectrometric apparatus such as an ICP or MIP analytical apparatus is particularly useful for detecting a trace amount of inorganic elements, and widely used in many fields including semiconductor, geological and environmental industries. For purposes of simplification, below is provided an explanation of an ICP-MS apparatus as an example of the plasma spectrometric apparatus of the prior art. FIG. 7 shows an example of a configuration similar to the conventional inductively coupled plasma mass spectrometer (ICP-MS apparatus) shown in FIG. 3 of Patent Literature 1.
In FIG. 7, the flow rate of gas, e.g., an argon gas 704, from a gas source (not shown) is controlled by a gas flow rate control part 703. A carrier gas from the gas flow rate control part 703 and a liquid sample 702 from a sample tank 701 are introduced to a nebulizer 705, and the sample 702 is nebulized. A spray chamber 706 is installed to the nebulizer 705 through an end cap 707. In addition, a make-up gas from the gas flow rate control part 703 is supplied to the spray chamber 706 through the end cap 707. Of droplets of the nebulized sample 702, droplets with a large particle diameter are attached to an inner wall of the spray chamber 706 and dropped, and drained to the outside from a drain hole 706a. The liquid drained from the drain hole 706a is sent to a drain tank 708 through a pump 715.
The sample nebulized in the spray chamber 706, and a mixed gas of the carrier gas and the make-up gas from the gas flow rate control part 703, that is, a gas generally-called an injector gas, are introduced to a plasma torch 709. The plasma torch 709 has a triple-tube structure including an inner tube to which the injector gas is introduced, an outer tube that is outside thereof, and an outermost tube that is further outside thereof. To the outer tube, an auxiliary gas from the gas flow control part 703 is introduced, and to the outermost tube, a plasma gas from the gas flow rate control part 703 is introduced. By inductively coupled plasma (ICP) 712 generated by a work coil 711 to which an electric current from a high frequency power source 710 is supplied, the sample 702 is ionized. Then, in a mass analyzer 713, elements in the ionized sample are separated and detected based on the mass-to-charge ratio, and the elements in the sample 702 and each element concentration are eventually obtained.
As a result of many years of technological development, it has become possible for ICP-MS apparatuses to detect a wide variety of elements at a more minute level. For example, it has become possible for ICP-MS apparatuses to quantify element concentrations at an excellent sensitivity level of one billionth (parts per billion, or ppb) or one trillionth (parts per trillion, or ppt), and a trace amount of silicon (Si), sulfur (S) or phosphorus (P), etc. contained in an analyte is also analyzed by mass spectrometry.
For example, Non-Patent Literatures 1-4 describe, respectively, performing mass spectrometry of a trace amount of silicon in an organic material such as polyamide; performing mass spectrometry of a trace amount of silicon in a metal material such as steel; performing mass spectrometry of a trace amount of silicon in a semiconductor such as GaAs semiconductor; and performing mass spectrometry of a trace amount of silicon contained in water such as ultrapure water. Further, Non-Patent Literatures 5-8 describe, respectively, performing mass spectrometry of sulfur or phosphorus contained in organic materials, oil products, pharmaceutical products, food, water, biofuels, metal materials, biological samples, high-purity reagents, geological materials, organic solvents, and others; performing mass spectrometry of a trace amount of sulfur in a semiconductor such as GeO2; performing mass spectrometry of a trace amount of sulfur in an organic material such as Bisphenol A; and performing mass spectrometry of a trace amount of sulfur in organic matrices such as fuels, biomaterials, and pharmaceutical products.